The Jet Propulsion Lab team's RoboSimian robot turns on a valve at a simulated disaster-response course during day one of the Defense Advanced Research Projects Agency (DARPA) Robotics Challenge finals in Pomona, California, June 5, 2015. (Photo by David McNew/Reuters)

Well before Corey Arnold ever thought about photography, he fished. As a child, he dressed as a fisherman for four consecutive Halloweens, and once brought a dead 3-foot Mako shark to school for show-and-tell. He knew he wanted to be a professional fisherman, even if he didn’t understand what that actually meant.

Global wildlife populations will decline by 67% by 2020 unless urgent action is taken to reduce human impact on species and ecosystems, warns the biennial Living Planet Index report from WWF (World Wide Fund for Nature) and ZSL (Zoological Society of London). From elephants to eels, here are some of the wildlife populations most affected by human activity. Here: The maned wolf is among the large mammals in the Brazilian Cerrado that are threatened by the increasing conversion of grasslands into farmland for grazing and growing crops. (Photo by Ben Cranke/Nature Picture Library/Alamy Stock Photo)

A wolf-like robot “Super Monster Wolf” stands beside a rice field to drive away wild animals that cause damages to crops in Kisarazu, Chiba prefecture, on August 25, 2017. The agricultural coopetative association JA Kisarazu-shi introduced the 65cm-long and 50cm-high robot recently on a trial basis which can detect wild animals such as boars and deers with an infrared ray sensor when they approach and intimidates them, flashing the red LED eyes and blaring 48 types of sounds including a wolf growl and human voice. (Photo by Toru Yamanaka/AFP Photo)

A man dressed up as a "Catrin", a Mexican character also known as "The Elegant Death", is pictured during a Catrinas parade in Mexico City October 31, 2015. (Photo by Carlos Jasso/Reuters)

A dog jumps into the air to catch a ball along the beach near the County Kerry village of Rossbeigh, Ireland, February 4, 2018. (Photo by Clodagh Kilcoyne/Reuters)

Model present creations by Emilia Wickstead for Matchesfashion.com during Australian Fashion Week, May 15, 2018. (Photo by Edgar Su/Reuters)

A photo taken from the International Space Station shows Hurricane Lane in the early morning hours near Hawaii, August 22, 2018. (Photo by Courtesy @astro_ricky/NASA/Handout via Reuters)